Process of preparing tetrakis-2-chloroethyl silicate



Patented Aug. 7, 1945 UNITED STATES PATENT OFFICE PROCESS OF PREPARINGTETRAKIS-Z CHLOROETHYL SILICATE Wilton I. Patnode and Robert '0. Saner,Schenectady, N. Y., asslgnors to General Electric Company, a corporationof New York No Drawing. Application May 14, 1942, sci-n1 No. 443,022

3Claims.

preparing tetrakis-z-chloroethyi silicate.

It was known prior to our invention that tetrakis-ethyl silicate couldbe prepared by reacting silicon tetrachloride with ethyl alcohol. It

was also known that silicon tetrachloride would SKOCHQCHaCDs by reactingethylene glycol with silicon tetrachloride. The compound was reported byTaurke as being a water-white liquid having a boiling point of 177-180"C. at 8 mm. pressure. In each of these reported reactions involving thechlorine atoms or the silicon chloride and the hydroxyl groups of thealcohols, hydrogen ,chloride is a gaseous reaction product. As four moleof hydrogen chloride gas is evolved for each mol of the tetraester orsilicic acid, provision must always be made for disposal of thisundesired product.

We now have discovered that tetrakis-2- chloroethyl silicate .may bereadily prepared, without the evolution of hydrogen chloride, by causingethylene oxide to react with silicon tetrachloride. The reaction betweenthe ethylene oxide and the silicon-tetrachloride maybe expressed by'theequa I g ride contains a small but apprecable concentration or hydrogenchloride, the dissolved hydrogen chloride probably behaves as a catalystfor the reaction. At least, the rate oi. reaction can be increased whendesired by increasingthe concentration ofthe hydrogen-chloride; However,as can be seen from the equation, no additional hydrogen chloride isformed or evolvedfduringthe reaction.

. In order that those skilled in the art bettermay understand how ourinvention may be carried into effect. the following specific'examplesaregiven illustrating the preparation 01' tetra-kis-z-chloroethyl silicate.I

. Example I Atwo-n'ecked flask of 1 liter capacity was equipped with (1)a water-jacketed bulb reflux chloride. was begun and the reaction vesselsurrounded by a warm water bath. Heat was applied at such a rate as tokeep the lower portion of the condenser (flooded. After ethylene oxidehad been introi, .duced for llbhours, no more silicon tetrachlo- 35ride-refluxed and. thetemperature rose to 70.

Since evenfreshly distilled 'silicontetracbio- The present inventionrelates to a process of a calcium chloride tube. and (2) an inlet tubereaching to the bottom of the flask. Three mols (510 8.) f redistilled81110011 tetrachloride boilin at 57-57.5 C. were placed in the flask.Ethylene 5 oxide was slowly. introduced through the inlet tube into theliquid silicon tetrachloride held at refluxing temperatures by means ofa hot plate.

After 15 hours no more reflux was observed at this rate of heating andthe temperature had risen considerably over 100, causing somediscoloration. At this point the heating unit was removed, and the gaswas bubbled through the reaction mass more slowly until the activechlorine content was reduced to 0.7% as shown by titration with aqueousalkali. This required an additional period of 15 hours. The product wasfractionated at reduced pressure (6.5-7 mm.) yielding about 900 grams oftetrakis-z-chloroethyl silicate and about 85 grams of a dark liq- 2 uidresidue boiling with decomposition at about 220 C. at 1 mm. pressure.

Example Ii Into a 1-liter, three-necked flask, bearing a water-cooledreflux condenser packed with glass beads, a thermometer and a capillarytube for the introduction of theethylene oxide gas, was placed '68 g.(0.4 mol) of redistilled silicon tetra- The slow addition of ethyleneoxide Beating the water bathto 80-90 caused the tem- Keeping the bathboiling. the addition of eth- -ylene oxide was continued for 1% hourslonger. 40 At this time the flow of ethylene oxide was stopped, andafter cooling, the flask and contents was found to have gained 72.7 g.in weight.

" Titration 01' a samplewith aqueous alkali indicated 0.14% activechlorine present. Distiliation in vacuo gave 102 g; (73.6%) orchloroethyl silicate, B. P. 153-154" at 2 mm. and 144-147 at 0.8 mm.

' a The reaction between the boiling silicon tetrachloride and theethylene oxide, proceeds slowly. at first. After approximately two'molsof ethylene oxide have been absorbed per mol of silicon tetrachlorldethe reaction proceeds much more rapidlyand with the evolution of so muchheat that no external heating is required to maintain condenser packedwith glass beads and fltted with the reaction temperature at -100. It isnotasence of the low-boiling silicon tetrachloride.

The reaction product is usually slightly discolored but a singledistillation at reduced pressure (1-5 mm.) is suiiicient to give a goodyield of from 73 to 87% oi. a water-white product. A small i'orerun,presumably or compounds of the type (RD)aB1C1a-4, is usually obtained,but no appreciable residue remains except, as in the case of Example I,when the reaction temperature allowed to rise above 100-110. I

Samples of chloroethyl silicate, sealed in vacuo, were maintained at50', 100 and 150 for thirteenth days. Although a slight discoloration ofthe samples kept at 150 and 100 was observed, decomposition into acidicfragments was negligible, as shown by titration of these samples with Iaqueous alkali. Experiments on the hydrolysis of this compound indicatedgreater reactivity than ethyl silicate, making the ehloroethylproductaparticularlyusetulmbstitutei'orethyior higher silicates in anyoi'their hydrolysis' wli- Whatweclaimas'newanddesiretosecureby lettersPatent oi the United States is:

l. The process of preparing tetrakis-2-chloroethyisilicate whichcomprises reacting ethylene oxide with silicon tetrachloride at anelevated temperature.

2. The process of preparing tetrahis-2-chloroethyl silicate whichcomprises reacting ethylene oxide with siicon tetrachloride at anelevated temperature in the presence c! a small amount oi hydrogenchloride catalyst.

3. The process or preparing tetrakis-2-chioroethyl silicate whichcomprises slowly introducing ethylene oxide into silicon tetrachlorideheld at reflux temperatures until no further refluxing is obtained,increasing the temperature 0! the reaction mass to 100' C. andcontinuing the addition of ethylene oxide until the reaction masscontains substantially no active chlorine.

WINTON I. PA'I'NODE. ROBERT O. BAUER.

